Showing papers by "University of Pittsburgh published in 1984"

Effects of therapy with cholestyramine on progression of coronary arteriosclerosis: results of the NHLBI Type II Coronary Intervention Study.

Abstract: In the National Heart, Lung and Blood Institute Type II Coronary Intervention Study, patients with Type II hyperlipoproteinemia and coronary artery disease (CAD) were placed on a low-fat, low-cholesterol diet and then were randomly allocated to receive either 6 g cholestyramine four times daily or placebo. This double-blind study evaluated the effects of cholestyramine on the progression of CAD as assessed by angiography. Diet alone reduced the low-density lipoprotein cholesterol 6% in both groups. After randomization, low-density lipoprotein cholesterol decreased another 5% in the placebo group and 26% in the cholestyramine-treated group. Coronary angiography was performed in 116 patients before and after 5 years of treatment. CAD progressed in 49% (28 of 57) of the placebo-treated patients vs 32% (19 of 59) of the cholestyramine-treated patients (p less than .05). When only definite progression was considered, 35% (20 of 57) of the placebo-treated patients vs 25% (15 of 59) of the cholestyramine-treated patients exhibited definite progression; the difference was not statistically significant. However, when this analysis was performed with adjustment for baseline inequalities of risk factors, effect of treatment was more pronounced. Of lesions causing 50% or greater stenosis at baseline, 33% of placebo-treated and 12% of cholestyramine-treated patients manifested lesion progression (p less than .05). Similar analyses with other end points (percent of baseline lesions that progressed, lesions that progressed to occlusion, lesions that regressed, size of lesion change, and all cardiovascular end points) all favored the cholestyramine-treated group, but were not statistically significant. Thus, although the sample size does not allow a definitive conclusion to be drawn, this study suggests that cholestyramine treatment retards the rate of progression of CAD in patients with Type II hyperlipoproteinemia.

Exploring the Concept of “Fit” in Strategic Management

Abstract: Although the concept of “fit” appears to be a central theme in strategy literature, it has been inadequately defined as it relates to strategic management. A conceptual scheme based on two underlying dimensions—the conceptualization of fit and the domain of fit—is proposed to highlight differences among six schools of thought. Use of the classificatory scheme for addressing theoretical and managerial issues while employing the concept of fit in strategy research is discussed

Biased estimates of treatment effect in randomized experiments with nonlinear regressions and omitted covariates

Abstract: SUMMARY Certain important nonlinear regression models lead to biased estimates of treatment effect, even in randomized experiments, if needed covariates are omitted. The asymptotic bias is determined both for estimates based on the method of moments and for maximum likelihood estimates. The asymptotic bias from omitting covariates is shown to be zero if the regression of the response variable on treatment and covariates is linear or exponential, and, in regular cases, this is a necessary condition for zero bias. Many commonly used models do have such exponential regressions; thus randomization ensures unbiased treatment estimates in a large number of important nonlinear models. For moderately censored exponential survival data, analysis with the exponential survival model yields less biased estimates of treatment effect than analysis with the proportional hazards model of Cox, if needed covariates are omitted. Simulations confirm that calculations of asymptotic bias are in excellent agreement with the bias observed in experiments of modest size.

ISIS—a knowledge‐based system for factory scheduling

Abstract: Analysis of the job shop scheduling domain has indicated that the crux of the scheduling problem is the determination and satisfaction of a large variety of constraints. Schedules are influenced by such diverse and conflicting factors as due date requirements, cost restrictions, production levels, machine capabilities and substitutability, alternative production processes, order characteristics, resource requirements, and resource availability. This paper describes ISIS, a scheduling system capable of incorporating all relevant constraints in the construction of job shop schedules. We examine both the representation of constraints within ISIS, and the manner in which these constraints are used in conducting a constraint-directed search for an acceptable schedule. The important issues relating to the relaxation of constraints are addressed. Finally, the interactive scheduling facilities provided by ISIS are considered.

Flow of a viscoelastic fluid over a stretching sheet

Abstract: This paper presents a study of the flow of an incompressible second-order fluid past a stretching sheet. The problem has a bearing on some polymer processing application such as the continuous extrusion of a polymer sheet from a die.

Venous bypass in clinical liver transplantation.

Abstract: A venous bypass technique (BP) that does not require the use of systemic anticoagulation is used routinely at our institution in all adult patients during the anhepatic phase of liver transplantation (LT). Complete cardiopulmonary profiles were obtained in a subset of 28 consecutive cases. During the anhepatic phase while on bypass, mean arterial pressure, central venous pressure, and pulmonary arterial wedge pressure were maintained at prehepatectomy levels. Oxygen consumption fell secondary to a decrease in temperature and the removal of the liver. Consequently, cardiac index fell without an increase in arterial-venous O2 content difference, reflecting adequate tissue oxygenation. Compared with 63 patients in a previous series given LT without bypass (NBP), the 57 total BP patients experienced better postoperative renal function (p less than 0.001), required less blood use during surgery (p less than 0.01), and had better survival 30 days after LT. The equivalency of 90-day survival in these groups results from the lack of effect of BP on the long-term survival of patients considered at high risk for metabolic reasons. BP patients at high risk for technical considerations, however, survived LT whereas NBP patients did not. BP offers other advantages important in establishing LT as a service-oriented procedure.

Point mutations close to the AUG initiator codon affect the efficiency of translation of rat preproinsulin in vivo

Abstract: To determine whether sequence context influences the ability of an AUG triplet to be recognized as an initiator codon by eukaryotic ribosomes, single nucleotide changes were introduced near the translational start site in a cloned preproinsulin gene Maximum synthesis of preproinsulin occurred when a purine, preferably adenosine, was located three nucleotides upstream from the initiator codon Adenosine is found most frequently in that position in natural mRNAs

Militarized Interstate Disputes, 1816-1976: Procedures, Patterns, and Insights

Abstract: This article offers an empirical description and discussion of interstate conflict behavior. The basis is a recently completed data set consisting of all recorded instances of threats, displays, an...

The location and morphology of preganglionic neurons and the distribution of visceral afferents from the rat pelvic nerve: a horseradish peroxidase study.

Abstract: Preganglionic neurons of the sacral parasympathetic nucleus (SPN) were located almost exclusively (98%) within the L6-S1 spinal cord segments. The SPN contained approximately 550 neurons of medium size (10 X 20 micron). These were mainly located in the intermediolateral gray matter and had dendrites that extended into the dorsolateral funiculus, along the lateral marginal zone of the dorsal horn, and medially into the dorsal gray commissure. Labeled dorsal root ganglion cells were almost all located (95%) in the L6 and S1 ganglia. An average of approximately 1,500 sensory neurons were found. These were small cells (17 X 25 micron) whose central processes entered Lissauer's tract from which two groups of collaterals emerged: 1) a prominent lateral pathway along the lateral margin of the dorsal horn that extended into the region of the SPN and also into the dorsal gray commissure, 2) a less prominent medial pathway extending around the dorsal margin of the dorsal horn to terminate in the dorsal gray commissure. These two collateral groups formed fiber bundles that were spaced by approximately 100 micron between centers when observed in the horizontal plane. A third afferent bundle, composed of rostrocaudally oriented fibers, was located in the sagittal plane immediately ventral to the central canal. Comparisons are made between the results in rats and the results of similar experiments performed in cats and monkeys.

Nonuniform recombination within the human beta-globin gene cluster.

Abstract: Population genetic analysis of 15 restriction site polymorphisms demonstrates nonuniform recombination within the human beta-globin gene cluster. These DNA polymorphisms show two clusters of high nonrandom associations, one 5' and another 3' to the beta-globin structural gene, with no significant linkage disequilibrium between the two clusters. The 5'- and 3'-association clusters are 34.6 kilobases (kb) and 19.4 kb long, respectively, and are separated by 9.1 kb of DNA immediately 5' to the beta-globin gene. For each of these three DNA regions, we have observed a relationship between nonrandom associations and physical distance between the polymorphisms. However, this relationship differed for each of these regions. On the assumption that the effective population size (Ne) is 5,000-50,000, we estimate the total recombination rate to be 0.0017%-0.0002% in the 5' cluster, 0.0931%-0.0093% in the 3' cluster, and 0.2912%-0.0219% in the 9.1-kb region between them. The beta cluster thus shows nonuniformity in recombination. Moreover, the recombination rate in the 9.1-kb DNA segment is 3-30 times greater than expected and is thus a hot spot for meiotic recombination.

Lymphocytes in the skin of patients with progressive systemic sclerosis. Quantification, subtyping, and clinical correlations.

Abstract: Mononuclear cells (MNC) present in the dermis of the forearm and in the blood of patients with progressive systemic sclerosis (PSS) were quantified and analyzed for subsets using monoclonal antibodies. The findings were correlated with cutaneous and systemic features of the disease. Total T lymphocytes and their subsets, B cells, and macrophages were enumerated in the skin samples of 21 patients with PSS. The dermal MNC infiltrates consisted mostly of activated T lymphocytes with a mean T helper/T suppressor (T4/T8) ratio of 2.4 +/- 1.3 SD. Few B1-positive or T6-positive cells (macrophages) were observed. There was no correlation between the skin or blood T4/T8 ratios and the degree of skin thickening. On histologic examination, 58 of 115 (50%) untreated patients with PSS had prominent dermal MNC infiltration. Significant correlations between the degree of MNC infiltration and both the degree (P less than 0.05) and progression (P less than 0.05) of skin thickening were observed. No correlations with other systemic disease features of PSS were noted. These results suggest that cutaneous T lymphocytes may play a role in mediating dermal sclerosis in PSS.

Baclofen in the treatment of trigeminal neuralgia: Double-blind study and long-term follow-up

Abstract: A double-blind crossover study of the effects of baclofen was conducted on 10 patients with typical trigeminal neuralgia. Baclofen significantly decreased the number of painful paroxysms in 7 of the 10 patients. An open trial in another 50 patients with trigeminal neuralgia refractory to or unable to tolerate carbamazepine showed that 37 (74%) were relieved of their attacks by baclofen, either alone (12 patients) or in combination with previously ineffective doses of carbamazepine or phenytoin (25). On long-term follow-up of one to five years (mean, 3.0 years), 18 of the 60 patients (30%) continued pain free while receiving baclofen; 10 (17%) went into remission after 3 to 6 months; 13 (22%) became refractory to baclofen after 1 to 18 months; and 2 (3%) elected operation despite a good response to baclofen. The results indicate that baclofen is a useful drug in the treatment of trigeminal neuralgia.

A flexible procedure for multiple cadaveric organ procurement

Abstract: Techniques have been developed which permit removal of the kidneys, liver, heart and other organs from the same donor without jeopardy to any of the individual grafts. The guiding principle is avoidance with all organs of warm ischemia. This is achieved by carefully timed and controlled infusion of cold solutions into anatomic regions, the limits of which are defined by preliminary dissection.

Factors influencing divestment decision-making: evidence from a field study

Abstract: This research investigates factors which influenced the corporate-level divestment decisions of large, diversified firms. Field research, including interviews with corporate executives of 40 large diversified firms, provided the data to test propositions developed from various literature sources. In general, thefindings from this research indicate that a business unit's strength, its relationship to other units in its firm and its parent firm's financial position compared to its competitors are important divestment influences, whereas other factors such as general economic conditions are not. Some of the findings are consistent with conventional management wisdom, but others are counterintuitive.

Training High-Performance Skills: Fallacies and Guidelines

Abstract: A high-performance skill is defined as one for which (1) more than 100 hours of training are required, (2) substantial numbers of individuals fail to develop proficiency, and (3) the performance of...

An exact solution for the flow of a non-newtonian fluid past an infinite porous plate

Abstract: The flow of an incompressible fluid of second grade past an infinite porous plate subject to either suction or blowing at the plate is studied. It is found that existence of solutions is tied in with the sign of material moduli and in marked contrast to the Classical Newtonian, fluid solutions can be exhibited for the blowing problem.

Long-term potentiation of hippocampal synaptic transmission affects rate of behavioral learning.

Abstract: Electrical stimulation techniques were used to produce a long-lasting potentiation of synaptic transmission in the hippocampus of naive rabbits. Animals were then classically conditioned. Long-term potentiation of the hippocampus before training increased the rate at which animals subsequently learned the conditioning task. This result has significance for potential cellular mechanisms of associative learning.

Kinked DNA in crystalline complex with EcoRI endonuclease.

Abstract: The 3 A electron density map of a co-crystalline recognition complex between EcoRI endonuclease and the oligonucleotide TCGCGAATTCGCG reveals that a tight, complementary interface between the enzyme and the major groove of the DNA is the major determinant of sequence specificity. The DNA contains a torsional kink and other departures from the B conformation which unwind the DNA and thereby widen the major groove in the recognition site.

Pathologic findings from the national surgical adjuvant project for breast cancers (protocol no. 4) X. Discriminants for tenth year treatment failure

Abstract: A search for prognostic discriminants of treatment failure in the tenth postmastectomy year was undertaken in 614 patients enrolled in protocol no. 4 of the National Surgical Adjuvant Project for Breast Cancers treated by radical mastectomy. Exploratory analyses of 38 pathologic and 6 clinical features disclosed 16 and 13 variables significantly related to nodal status and treatment failure, respectively. However, multivariate analyses with life tables adjusted or controlled for nodal status revealed that patients whose tumors measured less than 2 cm had a more favorable clinical course. All of the characteristics were also explored when patients were stratified according to numbers of nodal metastases, the most significant prognostic discriminant for disease-free survival in the tenth year. A germinal center predominance lymph node pattern and high histologic grade according to our conventional grading method were observed to adversely influence disease-free survival in patients with negative nodes. A strong trend in this manner was also observed with tumors greater than or equal to 2 cm and types 3 and 5 scar cancers. Histologic grade and tumor size were significantly recognized as discriminatory in patients with 4+ nodes but no factors were significantly observed in the group of patients with 1 to 3 positive nodes. A possible explanation for this inconsistency is discussed. For the most part, these factors were also encountered by us previously at the 5-year postoperative period. Only the presence of 13+ nodal metastases and types 3 and 5 scar cancers and cancers without scar appeared to discriminate success or failure between the fifth and tenth year. It is therefore concluded that nodal category, germinal center predominance, histologic grade, and tumor size, in the contexts noted, represent strong prognostic discriminants exerting a rather constant influence on disease-free survival at least to the tenth postmastectomy period. The prognostic value of categorizing those patients with 4+ positive nodes into subgroups with 4 to 6, 7 to 12 and 13+ is reaffirmed. The actual disease-free survival of patients in the tenth year was not strikingly different from that observed previously by us at 5 years in this cohort.

Clinical spectrum of connective tissue disease after cosmetic surgery. Observations on eighteen patients and a review of the Japanese literature.

Abstract: Connective tissue disease has been reported to occur following cosmetic surgery with injection of the foreign substances paraffin and silicone (human adjuvant disease). The clinical findings in 18 such patients and a review of 28 additional cases from the Japanese literature are presented. The patients were classified into 2 major groups: group I consisted of 24 patients with definite connective tissue disease--12 with scleroderma, including 8 with progressive systemic sclerosis (PSS), 6 with rheumatoid arthritis, 5 with systemic lupus erythematosus, and 1 with polymyositis; group II consisted of 22 patients with human adjuvant disease with some symptoms, signs, and laboratory abnormalities suggestive, but not diagnostic of a connective tissue disease. The occurrence of PSS is approximately three-fold greater than expected for all women believed to have undergone such surgery, and PSS developed primarily in individuals injected with paraffin. Prolonged exposure to the injected substance may play a role in the induction of these immunologic disorders.